Such connecting elements and fastening arrangements are used particularly in lightweight constructions, for example in aircraft construction. A sample field of application is the connection of seat rails to transverse beams of a floor in an aircraft. In the same way, other rails, for example guide or securing rails in an aircraft hold, can be connected to corresponding transverse beams.
The prior art substantially specifies two alternative connection concepts for connecting the usual support structures for floors in aircraft (seat rails in the longitudinal direction of the aircraft and transverse floor beams in the transverse direction of the aircraft), the seat rails and transverse beams being designed as H beams or C beams in this case:    a) The seat rails extend above the transverse floor beams. The lower flange of a seat rail is connected to the upper flange of a transverse beam by screws or rivets. A disadvantage of this type of seat rail fastening is the relatively great construction height required for this floor structure.    b) The seat rail is partially notched in the region where it is connected to the transverse beam, i.e. furnished with a lower recess in which the transverse beam engages. However, the stability of the seat rail is considerably weakened due to this recess, with the result that it can then only transfer minimal transverse forces and normal forces. In order to compensate for this weakness, complex connection elements must be provided which are able to transfer the transverse and normal forces which are applied via the seats and the load on the seats into the seat rail over the notched region. Even if the main bending moments in the seat rail arise in the middle between two transverse beams, the bending moments are not reduced to zero in the notched area, with the result that the upper flange of the seat rail, along with the top of the seat rail, is not usually able to transfer the moments which arise in this area. Relatively low bending moments also need to be transferred in this case by the connection elements or by a connection member bridging the notched region.            In the past different, concepts were developed for connection elements and connection members. In one of these concepts the transverse floor beam in the region of the connection to a seat rail is furnished with a local penetration through which a connecting element is passed. This connecting element is then connected securely, for example riveted, to the seat rail on both sides of the recess. A structure is created in this manner in which the seat rail and the transverse beam engage with one another.        
Flange bending of the transverse beam may arise with connection concept a) in the region where a seat rail is connected to the transverse beam and where the force is thus applied to the transverse beam, especially if transverse floor beams are designed to be extremely weight-saving, resulting in local strength problems in the transverse beam.
The problem of flange bending may arise in particular if transverse floor beams are produced from anisotropic materials, e.g. carbon fibre composite material (CFRP). The main loads on transverse floor beams arise in the y/z plane. Transverse beams made from anisotropic materials are therefore primarily made with sufficient rigidity to withstand this load. However, bending of the upper flange of the transverse beam around a transverse axis (y axis) occurs locally in the region where the seat rail is connected. To absorb this effect, angles may be attached to reinforce the region on the transverse beam or the transverse beam component is made rigid in local areas in order to withstand these loads. Both solutions require additional process steps which result in increased manufacturing costs. The structural weight of these local reinforcements must also be taken into account.
A further problem is that weight-optimised lightweight transverse beams tend to tilt in regions in which a flange is exposed to a compressive load. As the upper flanges are generally supported at the sides by the seat rail connections, the unsupported lower flange is especially at risk of tilting. In this case the lower flange slips forwards or backwards (in the longitudinal direction of the aircraft). Therefore, to enable weight-optimised transverse beams to be used in the floor of an aircraft, additional elements are often fitted into the aircraft floor to counteract this tilting effect. These elements also represent additional weight and increase installation costs.
A connecting element is described in DE 201 14 953 U1 which comprises a basic body in the shape of an equilateral triangle, a triangular fastening strap being arranged on each edge of this triangle by means of material bridges. The connecting line for the respective material bridges forms a bending edge.
This connecting element becomes a corner connector for a frame after bending down the fastening straps. The individual fastening straps are only connected to the basic body by means of the material bridges in each case. The fastening straps are not intended to be connected directly to one another.
A connection shoe which has a C-shaped cross-section for sheet metal profiles which are also C-shaped is known from DE 34 42 550 C1. This connection shoe has a strap on its front face at one end, this strap being bent downwards from the middle profile section, i.e. towards the two side legs. The C-shaped profile body of the connecting element is inserted into a C-shaped profile element. A further C-shaped profile element is then placed at right angles to the first profile element and flat against this element, the section of the connection shoe protruding out of the first profile element engaging with the second profile element and the vertically bent strap of the connection shoe coming into two-dimensional contact with the middle profile section of the second profile element. No dedicated fastening sections are provided for the connection shoe to be securely connected to the profile elements by fastening means.
A support construction made from rectangular hollow profiles is known from DE 103 29 017 B4, these profiles being connected to each other by means of external or internal connecting elements. In this case the hollow profiles face each other, but do not penetrate each other.
A connection between a post and beam described for use in facades from DE 38 38 220 C2, in which the transverse beam is inserted in a partially recessed post from two sides and connected to the post by a sort of dowel mechanism.